Effect of isopropanol co-product on the long-term stability of TiO2 nanoparticle suspensions produced by microwave-assisted synthesis

[Display omitted] •microwave-assisted hydrolysis for preparation of TiO2 nanocrystals as safe suspension.•microwave-assisted distillation of isopropanol deriving from Ti-alkoxides hydrolysis.•beneficial effects of isopropanol distillation on 5–8 nmTiO2 nanoparticles suspension.•TiO2 nanocrystals are a suitable phase mixture for NO conversion in photocatalysis. In this paper we evaluate the effect of isopropanol arising from the reagent Ti(O-iPr)4 on the long-term stability of nanoparticle size of TiO2 produced during a microwave assisted sol-gel synthesis. Different configurations of microwave apparatus have been considered: the synthesis was carried out both in vessel or flask, and both performing or not isopropanol distillation through a modified microwave apparatus. Results revealed that isopropanol distillation after a short reaction time provided suspensions with slightly smaller particle size, that also show longer stability over time, especially for syntheses carried out at certain temperatures. Reactions performed distilling isopropanol from vessel and flasks showed comparable results, superior to the corresponding suspensions obtained without distilling isopropanol. This study is intended to provide a useful contribution to those applications where the need for stable TiO2 suspensions is critical.